U.S. Pat. No. 4,837,339 to Sato (Sato '339) discloses the synthesis of 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride compounds represented by the below formula A:
where R1 represents a lower alkoxy group, and R2 and R3 each represents a lower alkyl group or a lower alkoxy group, said 4-substituted-1,2,3,6-tetrahydrophthalic acid anhydride being liquid. The above compounds from formula A can be made by a Diels Alder type reaction wherein a 2-substituted-1,3-butadiene is reacted with maleic acid anhydride to generate the compounds as shown in Formula A. The general reaction scheme is shown below:

The compounds generated by the above reaction are useful as starting materials for silicone-containing polyester resins, polyamide resins and addition type polyimide resins; silane coupling agents, particularly, coupling agents for polyimide resins; plasticizers for vinyl chloride resins or the like, curing agents for epoxy resins and the like.
However, the present above reaction scheme suffers from several drawbacks including relatively poor yields, and relatively poor control of regiochemistry. Moreover, because the above compounds are liquids, purification sometimes proves to be difficult. Further, the compounds of Sato '339 have stability issues. Thus, it would be desirable to be able to generate compounds that are similar to the above compounds that can be used effectively as starting materials for silicone-containing polyester resins, polyamide resins and addition type polyimide resins, silane coupling agents, and coupling agents for polyimide resins, as well as for plasticizers for vinyl chloride resins and similar compounds, and for curing agents for epoxy resins that do not suffer from the same drawbacks as the compounds as disclosed in Sato '339.